Here's my experience. I was an academic philosopher for many years, so conceptual thinking was and is an important part of my psyche. After stream entry, I found it very hard to think conceptually for a number of years. This could have been complicated by the fact that I suffered pretty bad trauma from the post-stream entry dark night, which took me a considerable amount of psychological work to overcome. However, I think it may have also been partly insight related.
My ability to think clearly slowly returned as I recovered from the trauma, but it didn't go back to my pre-stream entry analytic philosopher levels of clarity and sharpness until I reached certain milestones in my meditation practice. The first was around the beginning of 3rd path. I was on a weekend retreat and at one point in the retreat I suddenly started dis-identifying with what I'll call the "rational voice". This is the calm assured conceptually articulate voice of the philosopher in me. I had always been very strongly identified with this voice, considering it "me" more than almost anything else. Anyway, there was a point on the weekend where I suddenly experienced this voice as being spoken by something else. This was, initially, rather startling and fear inducing, but because I was on retreat, I went with it. This led into a DN cycle on this voice. During some of the dukka nanas my mind started being filled with streams of totally irrational verbal thoughts. I was like I had super tourretts for about 5 minutes. This further dissolved into non-sense syllables. It was like the Christians who speak in tongues (which as a spiritual practice makes a lot more sense to me now!). I think these were all ways that the rational/conceptual part of my mind was going through the insight cycle. After that retreat, I was much sharper and able to think clearly without the thoughts seeming to cause as much inherent suffering. However, there was still a sort of lingering difficulty concentrating on conceptual problems for long periods of time, as I had once been able to do easily.
About 6 months later, in late 3rd path, I started doing serious vipassana investigating of the formless realms. This had the unforeseen effect of super-charging my thinking process. Since then I've been able to think and write clearly for hours with little fatigue or stress. Intensive thinking, reading, and writing have become no more inherently stress inducing that going for a walk. I have two possible theories about this. The first is that the formless realms are the mind-spaces out of which conceptual thoughts emerges. By investigating them and thereby making them empty, it allows thoughts to arise and pass without generating attachments. The other possibility is that thinking involves concentration, and before investigating the jhanas, I was attached to concentration states. Hence, any activity which made my mind concentrated would start to trigger the dukka of strong craving for jhana. After investigating these states and at least partially clearing my attachments to them, I find I am able to concentrate (both on and off the cushion) with much less stress.
Avi Craimer